1. Field of the Invention
The present invention relates to a seat drive motor and a power seat system having the same. More particularly, the present invention relates to a seat drive motor, which includes a housing installed in a vehicle seat through a bracket, and also relates to a power seat system having the same.
2. Description of Related Art
For example, Japanese Unexamined Patent Publication No. H8-40119 discloses a lift mechanism of a vehicle power seat system. In the lift mechanism, a seat drive motor, which has a speed reducing mechanism, drives a threaded shaft to linearly and axially move the threaded shaft in a forward or backward direction. When the threaded shaft is moved in the forward or backward direction, a link member, which is connected to one end of the threaded shaft, is pivoted to vertically move a vehicle seat, which is connected to the link member, in an upward or downward direction. The speed reducing mechanism includes a worm and a worm wheel, which are received in a gear housing of the motor. The worm is secured to a rotatable shaft (a drive shaft) of the motor, and the worm wheel is meshed with the worm. A threaded hole penetrates through the worm wheel in an axial direction of the worm wheel. Threads of the threaded shaft are engaged with threads of the threaded hole of the worm wheel. When the worm wheel is rotated by the motor, the threaded shaft is axially moved in the forward or backward direction. One such power seat system has a rotation sensor, which is installed in the gear housing of the motor and measures revolutions per minute (rpm), i.e., a rotational speed of the worm wheel.
When the power seat system has the above structure, in which the rotation sensor for measuring the rpm of the worm wheel is provided in an interior of the gear housing of the motor, it is difficult to install the rotation sensor in the interior of the gear housing at the time of assembling the motor.
In order to ease the installation of the rotation sensor to the gear housing, for example, Japanese Unexamined Utility Model Publication No. 5-3022 teaches provision of the rotation sensor at an outer side of the gear housing of the motor. In one such seat drive motor, one end portion of the gear housing, which extends in a direction perpendicular to the rotational axis of the worm wheel, engages a bracket, and a recess is formed in the end portion of the gear housing, which extends perpendicular to the rotational axis of the worm wheel. The rotation sensor, which measures the rpm of the worm wheel, is arranged in this recess.
However, in the above seat drive motor, at the time of driving the motor, a thrust force of the worm wheel is repeatedly applied to the portion of the gear housing, to which the rotation sensor is provided. Thus, the portion of the gear housing, to which the rotation sensor is provided, is flexed and is deformed by the thrust force. This causes a short lifetime of the gear housing. To address the above disadvantage, it is required to increase a wall thickness of the portion of the gear housing, to which the rotation sensor is provided. When the wall thickness of the gear housing is increased to reinforce the gear housing, a weight of the gear housing is disadvantageously increased, and a size of the gear housing is also disadvantageously increased. Also, this results in an increase in material costs of the gear housing.